A new enzyme that synthesized glucose-l,6-P2 has been found in brain and red cells. It will be characterized as to distribution kinetic properties, regulatory factors, and mechanism. It is different from phosphoglucomutase. A phosphatase for glucose-l,6-P2 in brain will be similarly studied. Further studies on control of phosphofructokinase in red blood cells are planned. By varying the fructose concentration given to these cells the F6P level of the cell can be varied over a wide range due to the high Km of hexokinase for fructose. We have thus shown sigmoidal kinetics for F6P in determining the PFK rate. This will be extended with varying levels of metabolites in the cell such as ATP, ADP, Pi, and 2,3-DPG, to show their regulatory effects in the whole cell.